In an angular velocity sensor, a movable electrode and a fixed electrode are disposed on a support substrate so as to oppose to each other, and an applied angular velocity is detected on the basis of the change of the distance between the movable electrode and the fixed electrode as is attendant upon the application of the angular velocity.
In an angular velocity sensor such as a micro-gyro sensor of electrostatic drive/capacitance detection type, when an angular velocity is to be detected, a driving voltage is applied between a fixed electrode and a movable electrode for drive, thereby to generate a potential difference and to vibrate a movable portion in one direction parallel to the substrate surface of a support substrate. On this occasion, when the angular velocity is applied, the angular velocity detecting interval between the movable electrode and the fixed electrode as is provided in the movable portion changes in accordance with the applied angular velocity, and hence, an output corresponding to the angular velocity is generated on the basis of a capacitance change based on the change of the interval (refer to, for example, U.S. Pat. No. 6,151,966).
However, the interval between both the electrodes is changed, not only by the angular velocity, but also by an external acceleration, and a capacitance change based on the change of the interval attributed to the acceleration is also outputted. This output becomes noise for the gyro sensor, which ought to detect the angular velocity.
In order to reduce the external acceleration output, therefore, the prior art has adopted a method wherein two vibrators of identical shape are arrayed and driven in reverse phases, and the differential output between the capacitance changes of the two vibrators is derived, whereby the external acceleration output is canceled, and only the angular velocity output is obtained.
In the above case, it has been verified, however, that the method cannot attain a satisfactory canceling effect, but that it generates the output ascribable to the external acceleration. Thus, it is an important problem to reduce the output ascribable to the external acceleration, and a method for solving the problem is desired.